The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An engine of a vehicle is operated in a state where various components are coupled to each other, and a bearing is mounted on a portion at which components are coupled and operated, to reduce friction.
In FIG. 1, a portion at which a connecting rod 11 and a crankshaft are coupled to each other is illustrated. A big end of the connecting rod 11 is coupled to the crankshaft to surround a crank pin 12, and a bearing 13 is provided between the big end of the connecting rod 11 and the crank pin 12. In addition, a gap between the big end of the connecting rod 11 and the crank pin 12 is filled with motor oil to reduce friction between the big end of the connecting rod 11 and the crank pin 12 when the engine is operated. In a normal state (see FIG. 1), a gap between the bearing 13 and the crank pin 12 is small, and an oil film is formed between the bearing 13 and the crank pin 12 by the motor oil, so that noise and vibration are small.
However, we have discovered that when the engine is operated for a long period of time under abnormal conditions (e.g., foreign substance inflow, oil shortage, poor connecting rod journal machining state, etc.) (see FIG. 2) and in a state where the bearing 13 is abraded and damaged, a gap G between the bearing 13 and the crank pin 12 is increased and noise and vibration are generated by a knock of the connecting rod 11 and the crank pin 12 during operation of the engine.
When the above state is continued, as illustrated in FIG. 3, the bearing 13 has a seizure on the crank pin 12, and thus oil supply between the big end of the connecting rod 11 and the crank pin 12 is interrupted. When the engine is operated in a state where the bearing 13 is damaged on the connecting rod 11 as described above, damage to the bearing is progressed to seizure of the bearing and metal contact occurs on the bearing 13, the big end of the connecting rod 11 and the like, thereby generating noise and vibration beyond normal range. Also, the bearing 13 or the like is damaged.
When the bearing 13 is damaged, due to an increase in frictional resistance, a phenomenon of an engine stall a vehicle is generated. That is, when the bearing 13 is damaged, an output of the engine is reduced due to an increase in frictional resistance, and revolutions per minute (RPM) of the engine is increased when an accelerator pedal is operated to recover reduction of the output. We have also discovered that an increase in the RPM of the engine repeats a vicious cycle in which the frictional resistance of the portion on which the bearing 13 is installed is increased again. At this time, the temperature of the friction portion is increased due to an increase of the frictional resistance, seizure is accelerated as the temperature of the bearing 13 is increased, and the components adjacent to the bearing 13, i.e., the connecting rod 11 and the crank pin 12, are also damaged, which causes damage to the engine.
When seizure of the bearing 13 occurs as described above, this leads to an overall problem of the engine and causes a problem such as engine stall. This cannot be solved only by repairing or replacing any one of the components, and the entire engine had to repaired or replaced.
The contents described in Description of Related Art are to help the understanding of the background of the present disclosure, and may include what is not previously known to those skilled in the art to which the present disclosure pertains.